A known type of tobacco shredding apparatus comprises a rotary carrier for one or more knives which cut tobacco shreds, for use in making cigarettes, from the leading face of a continuous mass of compacted tobacco. The compacted mass is formed and the tobacco therein provided in compacted form by a feeding device comprising a pair of upper and lower feed conveyors which define a gradually narrowing or converging path extending from a source of threshed tobacco lamina to a comminuting station where the leading face of the compacted mass is squeezed between air cylinder pressure assisted upper and lower pressure applying elements and moves into the range of the orbiting knives.
In our prior U.S. patent application Ser. No. 215,006 filed Dec. 10, 1980 now U.S. Pat No. 4,369,797 , assigned to the assignee herein and the disclosure of which is incorporated herein by reference, there is described an improved procedure for feeding tobacco to the compacting pair of upper and lower feed conveyors. As set forth therein, a layer of tobacco first is formed wherein the tobacco is oriented substantially planarly of the layer, the tobacco is interleaved and the tobacco is substantially uniformly distributed across the layer. The tobacco layer then is densified and the leaves nested by applying gravitational and vibrational forces thereto while simultaneously conveying the tobacco towards the upstream end of the converging conveyors without substantially altering the orientation and juxtaposition of the tobacco in the layer. The densified layer then is fed onto the lower one of the converging conveyors without substantially altering the orientation and juxtaposition of the tobacco in the densified layer. In this way, the orientation and juxtaposition of the tobacco is maintained all the way from the initial formation of the layer to the cutters.
The formation and conveying of the tobacco in this manner to the compacting conveyors results in much less compaction being required to be effected on the tobacco layer for the same throughput of tobacco when compared with conventional systems, and much less pressure needs to be applied to the compacted tobacco presented to the cutter to prevent lamina pull-outs, when compared with conventional procedures.
Since less compacting force needs to be applied to the lamina by the conveyors and such compacting force impares the filling power of the cut tobacco, the gravity-induced precompaction and nesting which is effected in this invention preserves the filling power of the cut tobacco. In addition, since the gravity-compacted tobacco is subjected to physical force for a lesser period of time than is usual in the prior art, more of the filling power is preserved.
In one embodiment of the procedure described in our prior application, a vibrating translating conveyor is provided which extends substantially horizontally away from the upstream end of the compacting conveyors. A relatively thick layer of tobacco containing the quantity of tobacco desired to be fed to the cutting station is formed at the upstream end of the conveyor by showering tobacco, in the form of whole leaves or threshed lamina, uniformly over a length of the conveyor, so that the tobacco builds up to the required layer thickness in the longitudinal direction of movement of the conveyor. The tobacco in the relatively thick layer is oriented substantially planarly of the layer and is substantially evenly distributed across the width of the layer.
The tobacco layer is subjected to vibration on the conveyor by vertical reciprocation of the conveying surface as the layer is conveyed thereon by the conveyor towards to the compacting conveyors under the influence of the translating surface of the conveyor. The vibration causes the tobacco in the layer to densify without the use of any force other than gravity while the layer is transported by the translating conveyor towards the cutting station without substantially altering the orientation and juxtaposition of the tobacco in the layer.
This orientation and juxtaposition is maintained as the layer is transferred from the vibrating conveyor to the lower one of the converging conveyors. There is no change in speed of the tobacco from the initial formation of the tobacco layer all the way to the cutters, and hence there is no opportunity for the tobacco to change its orientation and juxtaposition.
This operation contrasts markedly with that set forth in U.S. Pat. Nos. 4,244,382 and 4,254,781, both to Thiele et al, wherein a stepped conveyor is used and the stepped conveyor is vibrated in two directions. The stepped form of the conveyor means that the speed of the tobacco particles abruptly changes as an initially-formed thin layer forms a thick layer at the step in the conveyor for feed to the compacting conveyors. In this prior art, the thick layer of tobacco particles required to be fed to the cutters is formed by tumbling of particles from the thin stream at the step to form the thick layer, thereby altering the orientation and juxtaposition of the particles. The conveyors set forth in this prior art are designed to handle stem material, wherein such manipulation may be tolerated. In the procedure of our prior application, a thick layer is formed from a shower of tobacco lamina or whole leaves wherein the tobacco particles are provided in their final orientation and juxtaposition.